Selective Approach toward Multifunctionalized Lactams by Lewis Acid Promoted PhSe Group Transfer Radical Cyclization

We have developed a regiospecific and highly stereoselective strategy for constructing the five-/six-membered monocyclic and bicyclic nitrogen heterocycle skeletons using PhSe group transfer radical cyclization of α-phenylseleno amido esters promoted by a Lewis acid (e.g., Yb(OTf)₃) under UV irradiation. We obtained 5-/6-exo-trig mode cyclization products for the N-allyl/homoallyl substrates, whereas the enamide substrate gave 5-endo-trig ring closure.